I also thought that f^-1(x) implied the inverse function of f(x), but our own Pre-Calculus textbook disagrees. I quote Section 3-4 of Glencoe's Advanced Mathematical Concepts: Pre-Calculus with Applications.

"If f(x) denotes a function, then f^-1(x) denotes the inverse of f(x). However f^-1(x) may not necessarily be a function. To graph a function or relation and its inverse, you switch the x- and y-coordinates of the ordered pairs of the function. This results in graphs that are symmetric to each other with respect to the line y = x."

Needless to say I was shocked when a colleague pointed this out to me today. I guess I should read the textbook more often.